1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, such as a copier, a printer, a facsimile machine, and a multifunction peripheral including these.
2. Description of the Related Art
Some of electrophotographic image forming apparatuses, such as a copier, a printer, a facsimile machine, and a multifunction peripheral including these, are equipped with a unit body (a process cartridge) into which a developing unit and a photosensitive element unit are integrated.
In such image forming apparatuses, the process cartridge needs to be periodically replaced with a new one due to running out of toner or deterioration of a part such as the photosensitive element unit. Furthermore, some of the electrophotographic image forming apparatuses use an LED head in an exposure device; in such image forming apparatuses, a user has to open an upper cover installed on top of the main body of the image forming apparatus to replace the process cartridge.
Further, the LED head is located on a trajectory of the process cartridge when it is taken out. Therefore, as a method to replace the process cartridge, conventionally, the user has to bring an LED into a state where it is retracted away from a mounting position after or at the same time that the user opens the upper cover installed on top of the main body of the image forming apparatus, in order to take out the process cartridge from the main body of the image forming apparatus.
That is, because of the short focal length of the LED head, it is necessary to place the LED head such that an area irradiated by the LED head is located close to a photosensitive element. Therefore, in the replacement of the process cartridge or in the handling of a jam, the LED head needs to be retracted away from the photosensitive element.
As a method to retract the LED head away from the photosensitive element, there is already known a method in which a retracting mechanism is provided, and retract the LED head is retracted from and brought into contact with the photosensitive element in conjunction with opening-closing movement of the cover. As an example of the retracting mechanism, a link mechanism may be installed at an end of the LED head in a main-scanning direction. Furthermore, conventionally, there is proposed an image forming apparatus configured to be able to position an LED head without backlash (Japanese Patent Application Laid-open No. 2008-020845). This image forming apparatus includes a sliding member which can move between a close position for bringing the LED head close to a photosensitive element and a distant position for holding the LED head away from the photosensitive element, a positioning body which has a shaft not parallel to a moving direction of the sliding member, and a guide face which is formed approximately parallel to a shaft direction of the positioning body.
However, if the retracting mechanism is installed, a user may sometimes touch the retracting mechanism.
In view of this, there is a need to provide an image forming apparatus that includes a retracting mechanism of an exposure device and a covering member for covering the retracting mechanism, and can position the exposure device with respect to a photosensitive element (an image carrier) even if backlash of the photosensitive element (the image carrier) in a main-scanning direction (a longitudinal direction) is generated in the exposure device.